causal loop with only auxiliary variables and other issues

[Noorgm]

I have a Vensim model that is supposed to model transit ridership increase based on traffic congestion, and there are several issues I’m facing with my model.
The idea is that the population is divided into two groups, a group that lives close to Transit (in Transit oriented Development (TOD) areas) and a group that doesn’t, each group has a portion of them with trips close to transit and and a group that has trips outside transit areas. This creates four groups each with a different likelihood to use the transit with their trips over a car.

The likelihood to use the transit is how the modal split is calculated and how the number of car trips vs Transit trips are calculated.

The main idea is when the number of car trips starts causing congestion the likelihood to use Transit for each group increase as transit becomes more comfortable.

The issues arise because I have a causal loop with only auxiliary variables (likelihood to use the transit -> modal split -> car trips -> congestion-> likelihood to use the transit).
The second issue is that the max likelihood to use the transit is 1 for each group and I am trying to increase it in increments when congestion is high by adding 0.05 to its value, which seem wrong and it goes above 1.

I feel like the model has many issues but I what I am aiming to model is peoples tendencies to move to Transit as congestion increases. Anyone knows the key to fix these issues?

[Administrator]

The issues arise because I have a causal loop with only auxiliary variables (likelihood to use the transit -> modal split -> car trips -> congestion-> likelihood to use the transit).

This cannot be quite correct. The "likelihood to use the transit" would at least be delayed by a day (if I'm in congestion, I suppose I could attempt to turn back and use the transit instead, more likely I'd use the transit the next day (or if congestion is high for a number of days in a row).

So I'd probably have "likelihood to use the transit" as a level. Increases/decreases based on the amount of congestion.

The second issue is that the max likelihood to use the transit is 1 for each group and I am trying to increase it in increments when congestion is high by adding 0.05 to its value, which seem wrong and it goes above 1.

If "likelihood to use the transit" was a level, you could have something like this.

increase in likelihood to use transit = min ( 1 - "likelihood to use the transit", 0.05)